Validating Whole Slide Imaging for Diagnostic Purposes in Pathology: Guideline from the College of American Pathologists Pathology and Laboratory Quality Center

Abstract

Context.-There is increasing interest in using whole slide imaging (WSI) for diagnostic purposes (primary and/ or consultation). An important consideration is whether WSI can safely replace conventional light microscopy as the method by which pathologists review histologic sections, cytology slides, and/or hematology slides to render diagnoses. Validation of WSI is crucial to ensure that diagnostic performance based on digitized slides is at least equivalent to that of glass slides and light microscopy. Currently, there are no standard guidelines regarding validation of WSI for diagnostic use.Objective.-To recommend validation requirements for WSI systems to be used for diagnostic purposes.Design.-The College of American Pathologists Pathology and Laboratory Quality Center convened a nonvendor panel from North America with expertise in digital pathology to develop these validation recommendations. A literature review was performed in which 767 international publications that met search term requirements were identified. Studies outside the scope of this effort and those related solely to technical elements, education, and image analysis were excluded. A total of 27 publications were graded and underwent data extraction for evidence evaluation. Recommendations were derived from the strength of evidence determined from 23 of these published studies, open comment feedback, and expert panel consensus.Results.-Twelve guideline statements were established to help pathology laboratories validate their own WSI systems intended for clinical use. Validation of the entire WSI system, involving pathologists trained to use the system, should be performed in a manner that emulates the laboratory's actual clinical environment. It is recommended that such a validation study include at least 60 routine cases per application, comparing intraobserver diagnostic concordance between digitized and glass slides viewed at least 2 weeks apart. It is important that the validation process confirm that all material present on a glass slide to be scanned is included in the digital image.Conclusions.-Validation should demonstrate that the WSI system under review produces acceptable digital slides for diagnostic interpretation. The intention of validating WSI systems is to permit the clinical use of this technology in a manner that does not compromise patient care.

Interinstitutional Whole Slide Imaging Teleconsultation Service Development: Assessment Using Internal Training and Clinical Consultation Cases

“…The adjusted WSI major discrepancy rate in our study of 2.7% (2 of 74) by case is similar to the Bauer et al 8 results of 1.65% (5 of 303) and to the Campbell et al 13 results of 1.5% (3 of 212) for primary diagnosis. The results of these studies and ours are notably better than the average agreement rates found in the Pantanowitz et al 17 statistical meta-analysis of the publications to date, given in the College of American Pathologists guidelines for WSI validation, which showed WSI to be 3% (89% versus 92%) less accurate than GS examination, which is noteworthy because the clinical trial presented here was on intrinsically more difficult, consultation cases. There are a number of potential explanations for these differences.…”

Validating Whole-Slide Imaging for Consultation Diagnoses in Surgical Pathology

“…4 Those guidelines suggested, among other things, that laboratories implementing WSI for diagnostic purposes should perform their own intraobserver variability (validation) studies, and that those studies should be appropriate for the intended clinical use of WSI in the laboratory. Validation studies should involve specimen preparations relevant to the intended use, and ''if a new intended use is contemplated, and this new use differs materially from the previously validated use, a separate validation for the new use should be performed.…”

Future perspectives of digital pathology

“…It should be noted that when making diagnoses by conventional microscopy, differences in the interpretation of individual cases can occur, which will increase to more problematic any specimen is found to be. Recommendations exist for using WSI systems in diagnostics including, amongst others, guidelines from the College of American Pathologists (CAP), the Digital Pathology Association and the Royal College of Pathologists [49]. According to CAP guidelines, internal quality control should be undertaken for any laboratory deciding to carry out digital diagnostics.…”